Desulfurization of carbonaceous solid fuels



Feb. 18, 1958 E. GORINETAL DESULFURIZATION 0F CARBONACEOUS soun FUELS Filed Aug. 11, 1955 EQUILIBRIUM CURVE FOR PHZS/ OVER 'SULFURCONTAINING PH CARBONACEOUS SOLIDS snyDm i f V II.

SULFUR IN CARBONACEOUS SOLIDS FIG. I

NET GAS WM. w

SOLIDS I INVENTOR8 GEORGE P. CURRAN, EVERETT GORIN, JAIIjIE/S D. BATCHELOR ATTORNEY DESULFURIZATION F CARBONACEOUS SOLID FUELS Everett Gorin, George P. Curran, and James D. Batchelor, Pittsburgh, Pa., assignors to Pittsburgh Consolidation Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Application August 11, 1955,'Serial No. 527,705

19 Claims. (Cl. 202-31) The present invention relates to the removal of sulfur from carbonaceous solid fuels. More particularly, it relates to the treatment of carbonaceous solid fuels at elevated temperatures in the presence of hydrogen gas and solid acceptors for hydrogen sulfide.

The presence of sulfur in carbonaceous solid fuels limits their use in metallurgical applications. In order to reduce the sulfur contamination of carbonaceous solid fuels, treatment of these fuels with reducing gases has been proposed. In co-pending U. S. application 423,6'13, now United States Patent 2,717,868, filed April 16, 1954, entitled Desulfurization of Low Temperature Carbonization Char, by Everett Gorin and Clyde W. Zielke, the desulfurization of carbonaceous solid fuels with recirculating hydrogen gas at slightly elevated pressures was described. Hydrogen sulfide gas, resulting from desulfurization of carbon with hydrogen gas, strongly inhibits additional desulfurization which occurs principally through further formation of hydrogen sulfide gas. To permit full use of the available hydrogen gas in desulfurization treatment, removal of hydrogen sulfide from the recirculating gas stream was required; to obtain adequate sulfur removal within feasible treatment times, elevated pressures were required for increasing the mass flow ratio of hydrogen to carbonaceous solids. Addition of extrinsic heat to the desulfurization zone was required.

According to the present invention, carbonaceous solid fuels containing sulfur are mixed with a solid material (herein termed an acceptor) which is capable of absorbing hydrogen sulfide. The mixture is treated with hydrogen gas at a temperature above 1100 F. whereby the hydrogen gas combines with the contaminating sulfur of the carbonaceous solid fuels to form hydrogen sulfide; the hydrogen sulfide is absorbed in situ by the hydrogen sulfide acceptor. Since the hydrogen sulfide is absorbed almost instantly upon formation, there is only a negligible partial pressure of hydrogen sulfide in the desulfurization zone for inhibiting the reactions whereby sulfur is removed from the carbonaceous solid fuels. The efiluent gases from the desulfurization reaction zone are rich in hydrogen content and may be recirculated directly to the desulfurization zone without further treatment. The reaction mixture of solids is separated into (a) product desulfurized carbonaceous solid fuel and (b) the solid acceptor containing accepted sulfur which may be regenerated and heated by contact with air to restore its hydro gen sulfide acceptor properties through elimination of Previously absorbed sulfur. The hot, regenerated acceptor, when mixed with relatively cool carbonaceous solid fuels preferably provides the heat necessary to raise the solids reaction mixture to a desulfurization temperature.

The present invention is applicable to non-caking carbonaceous solid fuels such as cokes and char. Coke from coal and liquid hydrocarbonaceous residues (pitch coke), coke breeze, low temperature carbonization char from coal and lignite are exemplary. The invention obviously is not applicable to caking carbonaceous solid fuels such ice as caking coal since the thermal treatment encompassed in our invention would cause these materials to become sticky and form .coked masses which would bind the acceptor solids, thus preventing their recovery for reuse in the process and also contaminating the resulting coke with the acceptor solids and any sulfur transferred from the coking coal to the bound acceptor solids. The invention, however, can be applied to the desulfurization of carbonaceous briquets containing caking coals where the thermal treatment is conducted to avoid severe caking and accompanying formation of large coke masses.

Any solid material capable of absorbing hydrogen sulfide at elevated temperatures in the presence of hydrogen gas and capable of rejecting absorbed sulfur when contacted under oxidative conditions at elevated temperatures is suitable as the hydrogen sulfide acceptor in the present invention. These materials preferably are comprised of a major portion of an inactive material serving as a carrier and support'for a minor portion of an active material. which reacts chemically with hydrogen sulfide to effect its removal from the gas phase in the desulfurization zone. The active ingredient in the acceptor sol-ids may include, for example, oxides of various metals such as calcium, manganese, zinc, iron, nickel, copper, lead and cobalt. Preferred oxides are calcium oxide and manganese oxide. Several of these exemplary active ingredients also may exist as free metals in their active form, such as zinc, iron, nickel, copper, lead and cobalt.

The desulfur'ization of the present invention is conducted at temperatures above 1100 F., preferably from about 1100 to about 1800 F. Some acceptor materials perform best at the high end of the range, others at the low end as will be pointed out hereinafter. With all .acceptors, however, an increase in temperature is accompanied by a decrease in H 5 absorption efficiency. This is inherently offset, however, since the effect of H 8 as a desulfurization inhibitor also decreases with increasing temperature.

Since the primary object of this invention is to prepare a low sulfur carbonaceous solid fuel, it is essential that the carbon consumption be minimized during the process. Carbonaceous solid fuels comprise moisture, volatile matter, fixed carbon and ash. The moisture and substantial bulk of the volatile matter are driven from the carbonaceous fuel during the present treatment at elevated temperatures. The fixed carbon is unaffected by the thermal treatment except insofar as it is consumed through reaction with steam and/or hydrogen.

The requisite presence of substantial quantities of hydrogen in the desulfurization gases inhibits carbon consumption via the carbon-steam reaction. At the lower temperatures of the desulfurizat-ion range, moreover. there is only a slight tendency for steam to react with the carbon. Thus carbon consumption through steam reaction is small.

The hydrogen-carbon reaction is limited throughout the desulfurization range at low pressures through inhibition from the methane contained in the treating gases. At higher pressures, the equilibrium concentration of methane gas is higher and more hydrogen-carbon reaction may occur. Even at higher pressures however, the continued recirculation of treating gases permits the methane concentration to attain the equilibrium value whereupon no further hydrogen-carbon reaction obtains. Thus it is possible according to this invention to carry out de'sulfurization without substantial loss of the fixed carbon originally contained in the'carbonaceous solid fuel. In fact, cracking of the-devolatilization products from the carboriaceous solid fuel even in'the presence of hydrogen may result in a net production of additional fixed carbon.

For the purpose of this invention, fixed carbon is defined in the usual manner, i. e., that part of the carbonaceous solid fuel (other than ash) which remains behind when the volatile matter is driven off. Regardless of the carbonaceous solid fuel undergoing treatment, the process should be conducted so that at least 90 percent by weight of the fixed carbon initially in the fuel being treated remains in the product solid fuel. Consumption of more than 90 percent of the fixed carbon in the present process is wasteful and results in a product having an excessive fraction of ash.

The source of the hydrogen-rich treating gas in the present process preferably is the devolatilization gas evolved when carbonaceous solids are exposed to elevated temperatures, i; e. higher than any temperature to which the carbonaceous solid fuel has been previously exposed. When devolatilization gas is insufiicient, an extrinsic source of hydrogen gas may be provided.

For a clear understanding of the present invention, its

objects and advantages, reference should be had tothe following detailed description and accompanying drawings in which:

Figure 1 is a graphical illustration of the inhibition of carbonaceous solid fuels desulfurization by hydrogen sulfide; and

Figure 2 is a schematic illustration of apparatus adapted to carry out the present invention.

The equilibrium curve of Figure 1 shows the ratio of hydrogen sulfide partial pressure to hydrogen partial pressure existing at any one temperature in equilibrium with a typical sulfur-containing solid product from coal carbonization. The curve has the same general configuration as those reported for coke by Powell, J. A. C. S. 45, 1, l-l5 (1923). The curve has the same general shape throughout the temperature range 1100 to 1800 F. However, within the range, the curve shifts upwardly at in creased temperatures. When the ratio is below that of the curve of Figure 1, sulfur will be removed from the solids by the treating gas, forming hydrogen sulfide. When the ratio is above the curve of Figure 1, sulfur will be deposited upon the carbonaceous solids from the hydrogen sulfide of the gas. At gas concentrations on the curve of Figure 1, there is no net transfer of sulfur from gas to solids or from solids to gas.

The sulfur existing in carbonaceous solids is seen to be of three primary types.

(a) Readily removable sulfur-0rganically bound.- Generally 50 percent or more of the sulfur existing in low temperature carbonization char, for example, is organically bound sulfur which may be removed readily by treatment of the carbon solids with a hydrogen gas containing appreciable quantities of hydrogen sulfide. By representing the readily removable organically bound sulfur as C=S, the equilibrium shown therefor as the rising portion of the curve in Figure 1 may be written (b) Inorganically bound sulfur-principally as iron. sulfide.-A substantial portion of the sulfur contained in low temperature carbonization char, for example, exists as iron sulfide. Sulfur in this form can be readily removed by treating the char with pure hydrogen gas. Nevertheless, the equilibrium ratio of hydrogen sulfide to hydrogen is quite low and very small quantities of hydrogen sulfide will inhibit the transfer of sulfur from solid to gas. This equilibrium value is represented in Figure 1 as the horizontal portion of the curve. The height of the plateau d corresponds to the ratio of H S to H in equilibrium with the carbonaceous solids at the stated temperature. The length of the plateau corresponds to the amount of inorganic sulfur in the char. At 1350 F., for example, 0.12 volume percent of hydrogen sulfide in hydrogen gas is the equilibrium value; At 1600 F., 0.28 volume percent of hydrogen sulfide in the hydrogen gas is the equilibrium value. By representing the inorganically bound sulfur as FeS, the equilibrium shown in Figure 1 therefor may be Written FGS+HZ H2S+FC (c) Di/jicultly removable sulfurprincipally organically bound-Sulfur also exists in carbonaceous solids in the form of refractory organic material and various inorganic sulfides. While this sulfur theoretically could be removed by treatment with pure hydrogen gas, nevertheless even minute traces of hydrogen sulfide are sufiicient to inhibit the transfer of sulfur from solid to gas. Thus removal of this sulfur, represented by the rising portion from the origin of the curve of Figure l, is not practicable under feasible processing conditions.

The influence of hydrogen sulfide on the desulfurizing capacity of treating gases is of major importance.

We have found that the ultimate desulfurization which can be achieved at any temperature depends upon the ratio of H 8 to H in the treating gases without regard to the absolute pressure of the reaction system. Greater absolute pressure increases the rate of desulfurization, but does not affect the ultimate level of sulfur in the treated solids. We have found that in accordance with our present invention satisfactory desulfurization rates may be achieved at temperatures above 1100 F. with atmospheric pres sure treatment. Higher pressures accomplish the same desulfurization in shorter time. We prefer to carry out desulfurization at a pressure of l to 6 atmospheres absolute.

We have found that the hydrogen sulfide content of treating gases can be maintained at a minimum level by admixing the carbonaceous solids undergoing treatment with about an equal weight of solid acceptor. In this combination, any hydrogen sulfide formed as a product of the desulfurization reaction is removed by the acceptor in situ almost immediately upon formation whereby the hydrogen sulfide content of the treating gases can be maintained at an almost negligible value.

Accordingly, by limiting the hydrogen sulfide content of the treating gases to a value below the curve of Figure 1 corresponding to the readily removable, organically bound sulfur and the inorganic sulfur, a driving force for sulfur removal may be maintained throughout the desulfurization zone; Removal of substantial quantities of sulfur from the carbonaceous solids may be achieved thereby.

The solid acceptor should have a greater afiinity for hydrogen sulfide than those materials with which the sulfur is bound in the carbonaceous solid. The equilibrium value for the ratio PH S PH for the acceptor at the desulfurization temperature should be lower than the value shown in the curve of Figure l for the sulfur content desired in the product carbonaceous solid. In order to permit its subsequent separation from the desulfurized carbonaceous solids, the acceptor should have a size consist dilfering from that of the carbonaceous solids. The acceptor should be resistant to abrasive degradation at elevated temperatures. The acceptor should be a material which can be readily regenerated from its sulfur-containing form into a state where'it will once more absorb hydrogen sulfide.

A preferred acceptor for our desulfurization process is lime in the form of calcined dolomite or lime impregnated on an inert, non-acidic carrier such as magnesia or magnesite. Another preferred acceptor is manganese oxide impregnated on an inert carrier.-- Qther suitable acceptors include zinc oxide, nickel oxide, cobalt oxide, copper oxide, lead oxide and iron oxide. Suitableporous carriers for these impregnated oxides include silica, alumina, silicon carbide, silica-alumina, magnesia, natural clay pellets and the like. In, general basic supports such as. magnesia or silicon carbide are preferred. Amphoteric and acidic oxides may be employed if regeneration conditions be selected to avoid excessive reaction between the impregnated acceptor ingredient and the support.

The inert carrier has several functions in our present process. Firstly the inert carrier is an abrasion-resistant, yet porous material which can be moved through the process without excessive. degradation. Thus the active acceptor ingredient, retained. within the porous mass of the carrier solids, is protected from loss and attrition. Secondly the inert carrier is used to effect more nearly homogeneous admixture of the carbonaceous solids and the active acceptor ingredient. Since the. sulfur content of carbonaceous solids is about two percent of their weight, a substantial stoichiometric excess of active acceptor ingredient alone. would amount to a. small fraction of the bulk of the carbonaceous solids; dispersal of the active ingredient also would. be difficult. However where the active ingredient is itself uniformly dispersed upon an inert carrier solids, the. bulk of impregnated carrier solids can be made about equal to that. of. the carbonaceous solids, permitting ready mixing of the two materials and hence a uniform distribution of the active acceptor ingredient throughout the carbonaceous solids. Thirdly, the inert carner functions. as. a. heat carrying medium which absorbs heat during. the exothermic regeneration of the active ingredient and thereafter releases heat to the carbonaceous solids entering the desulfurization zone. The heat capacity of the stoicbiometric quantity of the active acceptor ingredient above is negligible; however the heat capacity of the. inert carrier. can be sufficient to permit carryingout the present process without resort to extrinsic heat. sources and also to; effect release of devolatilization gases from. the carbonaceous solids within the actual desulfuriza-tion zone.

Desulfurization according to the present invention depends upon the, ability of the hydrogen sulfide acceptor to maintain the ratio PHQS at a value below the curve of' Figure 1.. Four reactions may occur within the desulfurization zone as-followsz The desired Reaction 4 for'removing sulfur from the carbonaceous solids depends upon the value K; which is plotted in Figure 1. For continuedsulfur removal from carbonaceous solids, the mol fractionof H 5. in. the treating gases must be maintained ata low value by. continuous removal of H S from the gas via Reaction 2 or 3, depending upon whether the acceptor exists as a free metal or as a metal oxide.

With the readily reducible oxides such as iron, copper,

6 and nickel, the value K is high and hence the Reaction 2 does not occur in the hydrogen-rich environment of the present invention; instead Reaction 3 predominates to reduce the mol fraction of H 8 in the treating gases. The quantity of steam thus is not important provided the conditions are conducive to Reaction 1.

However, With the more diificultly reducible oxides such as calcium, manganese and zinc, the value K is low; hence the equilibrium K determines the extent to which the mol fraction of H 8 may be reduced in the treating gases. Thus with difiicultly reducible oxides the relative quantities of the primary gases in the system H 0, H 8 and H must be regulated for optimum results. This can be accomplished readily *by removal of steam from the recirculating gases, if necessary.

The generalized flow sheet of Figure 2 illustrates the manner in which the present invention is carried out in a continuous manner. A desulfurization zone 10 receives carbonaceous solids containing sulfur through conduit 11 and regenerated acceptor solids through conduit 12. A hydrogen-rich treating gas consisting essentially of 'hydrogen is introduced into the desulfurization zone 10 through a conduit 13. Additional gases, consisting esscntially of hydrogen gas are autogenously produced through devolatilization of the carbonaceous solids at the elevated temperature of the desulfurization zone 10. Under preferred operating conditions the autogenously produced devolatilization gases will be in sufficient quantity to provide the full hydrogen requirements for desulfurization so that extrinsic hydrogen production is not required. The preferred absolute pressure is selected to provide about one atmosphere partial pressure of hydrogen gas where devolatilization gases are to supply the hydrogen requirements. Higher pressures reduce the quantity of devolatilization gases evolved from the carbonaceous solids and also tend to increase the fraction of methane in the gases, i. e., to reduce the fraction of hydrogen. A typical char produced by fluidized carbonization of Pittsburgh seam coal at 950 F. yields devolatilization gases containing 58.6 percent hydrogen and 24.8 percent methane at 1.3 atmosphere and 1350 F. The same char yields devolatilization gases containing 48.7 percent =hydrogen and 32.9 percent methane at 3 atmospheres and 1350" F.

During passage through the desulfurization zone. 10, the treating gases remove sulfur from the carbonaceous solid forming hydrogen sulfide.

The H 8, upon formation is at once absorbed by the solid acceptor and removed from the gas phase. With solid acceptors in the oxide form, water results from the H absorption H S+Acceptor oxideacceptor su1fide+H O With solid acceptors in the metallic form, the hydrogen used to pick up sulfur from the carbonaceous solids is restored to the gas phase.

H S+Acceptor (metal)- acceptor sulfide+H Gases are recovered from the desulfurization zone- 10 through a conduit 14 and recirculated through conduit 13 for further contact with carbonaceous solids undergoing desulfurization. A not product gas is removed through a conduit 15.

When steady-state conditions have been established in a continuous system, the gases entering the desulfurization zone through conduit 13 have the same composition. as those leaving through conduit 14. Thus, since there is no net change in composition during the process, the treating gases may be entirely eliminated in some instances, although their presence as a transfer, medium greatly accelerates the transfer of sulfur from the carbonaceous solids to the solid acceptor to. admit extensi desulfurization within feasible contact time.

than the equilibrium sulfur value of the selected acceptor.

This factor will be discussed further hereinafter in relation to the use of iron oxide as acceptor. Where the hydrogen partial pressure of the treating gases is about one atmosphere or greater, satisfactory desulfurization can be achieved by subjecting the carbonaceous solids to the desulfurizing conditions of this invention for a period of one hour or less. Increased absolute pressure, as already pointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurization zone 10 as product through a conduit 16, sulfide acceptor is removed through conduit 17 and passed to an acceptor regeneration zone 18. Air is introduced into theregeneration zone 18 through a conduit 19 to raise the temperature of the acceptor through combustion of sulfur along with a portion of the carbonaceous solids adhering thereto and to remove sulfur therefrom through oxidation to sulfur dioxide.

Acceptor sr1lfide+O acceptor oxide+SO +heat Hot flue gases containing sulfur dioxide are removed from the regeneration zone 18 through a conduit 20. Regenerated acceptor is returned to the desulfurization zone through the conduit 12.

The carbonaceous solid material used in the present process preferably is low temperature carbonization char, i. e., the solid residue which remainsfollowing distillation of coal under low temperature carbonization' conditions. In general, low temperature carbonization-of coal iscarried out in the temperature range of about 800 to 1400 F., usually 800 to 1000" F. The char product is a low density, friable, solid material constituting more than 60 percent by Weight of the total products of the process. The invention also is applicable to the cokes produced under low temperature conditions from materials other than coal, for example, pitch cokes, petroleum-cokes, and solid residue from low temperature carbonization of lignites and the like. Preferably the carbonaceous solids should not have been exposed to a temperature higher than that of the desulfurization zone prior to the present treatment in order that the solid material retains sufficient volatile matter to supply autogenously the hydrogen requirements for the desulfurization reaction. Exposure to higher temperatures also reduces the lability of the sulfur and makes its removal more difiicult. At low temperatures in the desulfurization range it may be necessary to add extrinsic hydrogen gas to the system where de' volatilization is insufficient to supply autogenously the hydrogen requirements. Other materials, including metallurgical coke can be desulfurized by the present process provided an extrinsic source of hydrogen gas is available.

Calcium oxide Using lime as an illustrative example, our present process will be described in greater detail with reference to Figure 2. V I

Carbonaceous solids entering the desulfurization zone 10 are at an elevatedtemperature whichis preferably less than that of the desulfurization zone. naceous solids are intimately admixed with regenerated acceptor solids containing lime which are at an elevated temperature above that of the desulfurization zone. Intimacy of the admixture will be promoted if about equal quantities of the two solids are employed. The thermal interchangebetween the hot regenerated acceptor and the carbonaceous solids should provide a mixture of the two materials at the desired desulfurization temperature. Additional means for furnishing supplemen tary heat to the desulfurization zone may be. provided.

The size consist of carbonaceous solids should difi'er The carbo- 8 from the size consist of the regenerated lime acceptor to permit separation of the two materials following the present treatment. In the preferred processing modification of this invention the carbonaceous solid material has a fluidizable size consist, e. g., the carbonaceous solid will pass through a 14 mesh Tyler standard screen. The solid acceptor in the preferred embodiment takes the form of pellets having a diameter of /1 inch or greater.

Treating gases containing hydrogen pass through the mixture of carbonaceous solids' and acceptor forming hydrogen sulfide.

The hydrogen sulfide immediately upon formation reacts with the lime to form calcium sulfide and steam, thereby eliminating hydrogen sulfide from the treating gases.

The overall desulfurization reaction is c=s +H +CaO -0 +H O+CaS Thus throughout the desulfurization zone, continued transfer of sulfur from carbonaceous solids to gas is possible because the quantity of hydrogen sulfide in the gas phase is maintained at a level below that of the equilibrium curve of Figure 1. The sulfur is immediately retransferred from the gas phase to the lime which has a greater afiinity for sulfur than does the carbonaceous solid.

Gases leaving the desulfurization zone through the conduit 14 contain a major quantity of hydrogen gas and contain, in addition, methane, carbon dioxide, carbon monoxide, small quantities of steam and traces of hydrogen sulfide. In the preferred embodiment, incoming carbonaceous solids continuously produce additional hydrogen gas through 'devolatilization; hence a net product gas is continuously withdrawn through the conduit 15. The remainder of the gases is recirculated to the desulfurization zone for further treatment of carbonaceous solids. Should the incoming carbonaceous solids produce insufiicient hydrogen gas to perpetuate the reaction, additional hydrogen may be supplied to the conduit 13 from an extrinsic source. Alternatively, the gas in the conduit 13 may be passed in whole or in part through a high temperature methane reformer (not shown) to generate additional hydrogen.

In the acceptor regenerator, calcium sulfide is con tacted with air at a temperature of the order of 1800- 2000 F. for regeneration. The necessary heat may be supplied through combustion of sulfur along with a portion of the carbonaceous solids which adhere to the acceptor.

In the case of lime as an acceptor, sulfates are formed in the regeneration process in the presence of air due to the reactions.

When the lime acceptor is advanced to the calcium sulfate form, no furtherelimination of sulfur from the acceptor molecule is possible through oxidation alone. Sulfate formation can be suppressed by regeneration at extremely high temperature. It is undesirable to return calcium sulfate to the desulfurization zone since in this form it will consume hydrogen therein and disturb the sensitive hydrogen balance of the overall system.

However, the calcium sulfate can be decomposed in the absence of air as follows:

% CaSOH-Mz CaS CaO+SO Thus, where lime is selected as the acceptor, it is preferable to employ two regeneration vessels to permit oxidation of a portion of the calcium sulfide in one and to decompose in the other vessel in the absence of air any'sulfates formed, in the first vessel through reaction with calcium sulfide by the reaction listed immediately above. As an alternative to the two-vessel lime acceptor regeneration technique, the quantity of calcium sulfate in regenerated acceptor may be minimized by providing a carefully controlled air supply to a single vessel regenerator whereby only incomplete oxidation of the calcium sulfide occurs. If the oxygen of air be completely consumed within the regenerator bed, the reaction between sulfate and sulfide can be achieved.

The regenerated acceptor is returned to the desulfurization zone for further treatment of carbonaceous solids. The weight ratio of acceptor solids to carbonaceous solids is determined by the thermal balance of the system and by the. stoichiometry of the desulfurization zone reactions.

For a preferred system which does not require additional extrinsic heat, the sensible heat of regenerated acceptor should balance the sensible heat required to raise the temperature of incoming carbonaceous solids to the, desired desulfurization level. The quantity of lime which must be provided on the acceptor solids is determined by the stoichiometry of the desired desulfurization. Preferably a substantial excess of the lime should be maintained in the desulfurization Zone at all times to assure removal of hydrogen sulfide from the treating gases.

When lime is used as acceptor in the form of calcined dolomite, it is preferred that the dolomite be calcined at about 2100 F. to improve its physical strength and resistance to physical degradation. In its preferred form, however, the acceptor solids are particles of an inert, non-amphoteric carrier impregnated with from about 2 to about 20 percent by weight of lime.

We have also found that basic slags produced in metallurgical processing contain lime distributed on a porous, inert material which is resistant to abrasion. Carefully screened particles of these basic slags may be employed as the acceptor solid in the present invention. Open hearth slag, for example, has been found to be satisfactory.

To illustrate the operation of the present invention,

the treatment of low temperature carbonization char derived from high sulfur, Pittsburgh seam coal will be described. The char, produced in a fluidized low temperature carbonization process, is available in finely divided form- (i. e., capable of passing through a 14 mesh Tyler standard screen) at 950 F. The char contains 2.53 percent sulfur and 15 percent volatile matter by weight. One ton of this char at 950 F. is mixed with 478 pounds of regenerated (previously calcined) dolomite. The re generated dolomite contains 174 pounds of CaO and 132 pounds of 02150 Extrinsic heat is provided to elevate the mixture to 1300 F. for desulfurization in the presence of a recirculating gas stream consisting essentially of hydrogen gas. Gas-to-solids contact is continued at atmospheric pressure. for one hour. Thereupon, 1700 pounds of product desulfurized char are recovered having a sulfur content of 0.66 percent by weight. The loss in weight of char is attributable to desulfurizationand devolatilization. 436 pounds of spent acceptor are recovered including 159 pounds of Gas and 105 pounds of CaO. The spent acceptor is regenerated at 1800 F. to produce once more the 478 pounds of regenerated dolomite, sufficient for treatment of another ton 'of char. Small quantities of additional calcined dolomite are added to the system to compensate for processing losses of the acceptor. The regeneration step just described is typical of those wherein no attempt is made to minimize the calcium sulfate content of the acceptor solids. The measures already discussed will permit substantial reduction in the quantity of calcium sulfate contained in the recirculation regenerated dolomite.

It has been shown in the. example that low temperature carbonizati'on char having. a, sulfur content of 2.53 percent by weight can be treated in the present process at atmospheric pressure to produce a char product having only 0;66 percent sulfur by weight. Thus a carbonaceous solid fuel; suitable for use in applications which place a premium on low sulfur content can be prepared fromfa high sulfur content starting material.

Manganese oxide Manganese oxide is. a preferred acceptor in the present process because of the extremely low equilibrium ratio of hydrogen sulfide to hydrogen exhibited by manganese sulfide at desulfurizing temperature. In the preferred form from about 2 to about 20 per-cent by weight of manganese oxide is impregnated upon an amphoteric oxide carrier. Alternatively, theacceptor may be a high manganese content slag obtained from metallurgical processing. Such slag also contains lime which serves as acceptor. Manganese oxide exhibits a strong afiinity for hydrogen sulfide even at low temperatures in the preferred desulfurization range of 1100-1800 F. The manganese. oxide desulfurization reaction is Regeneration of the manganese sulfide can be carried out at temperatures as low as about 1400 F. as follows:

Regeneration always results in formation of some higher oxides of manganese such as Mn O in addition to the desired MnO. At temperatures below about 1500 F., M11203 is produced in the presence of excess air. Thus higher oxides of manganese are undesirable in the desulfurization zone since they consume hydrogen, thereby disturbing. the sensitive hydrogen balance of the overall system.

Regeneration of the manganese sulfide also results in formation of undesirable sulfates.

Splfate similarly consumes hydrogen nonproductively in the desulfurization zone.

The formation of manganese sulfates can be minimized easily by conducting the regeneration of manganese acceptors at temperatures above about 1500 F. Operation above about 1500 F. also prevents formation of higher oxides than Mn O The hydrogen consumption corresponding to the reduction of Mn O to MnO is small.

Lower temperature operation in the range of 1300- 1500 F. also is possible with minimum formation of both sulfate and higher oxides. This may be accomplished by incomplete regeneration of the sulfide using a deficiency of air as already described in connection with lime regeneration, i. e., the manganese is regenerated by the reaction The use of manganese oxides as acceptor in the present invention will be illustrated with a description of the treatment of low temperature carbonization char derived from high sulfur Pittsburgh seam coal. The char, produced in. a'fluidized low temperature. carbonization process, contains2.53 percent sulfur and 15 percent volatile matter: lay-weight. One ton of char at 950 F. is mixed with 303:8. poundsof acceptor comprising alumina having manganese oxidesimpregnated thereon. Fresh acceptor contains 324 percent by Weight of manganese (in oxide form) on alumina. Under'the steady-state conditions of the present process, the regenerated acceptor includes 135 pounds of MnO and only negligiblequantities of manganese sulfate at a regeneration temperature of 1600 F. The described mixture of char and acceptor requires the addition of some extrinsic heat to attain a desulfurization temperature of 1300" F. for treatment with a recirculating gas stream consisting essentially of hydrogen gas. Following gas-to-solids contacting for a period of one hour at atmospheric pressure, 1700 pounds of product desulfurizcd char are recovered having a sulfur content of 0.68 percent by weight. The loss in weight of the char is attributable to desulfurization and devolatilization. 3048 pounds of sulfided acceptor are recovered including 106 pounds of manganese sulfide and 39 pounds of manganese oxide. The sulfided acceptor, on regeneration with air at 1600 F., reproduces the 3038 pounds of regenerated acceptor previously described, sufficient for treatment of another ton of char. Small quantities of additional acceptor maybe added to the recirculating system to compensate for processing losses.

This example illustrates that low temperature carbonization char having a sulfur content of 2.53 percent by weight can be treated in the present process at atmospheric pressure to produce a char producthaving only 0.68 percent sulfur by weight.

Zinc oxide 7 Another acceptor suitable in the present process in the lower range of desulfurization temperature is zinc oxide which has been impregnated upon aninert amphoteric oxide carrier such as alumina. From about 2 to about 20 percent by Weight of zinc oxide on the carrier is suitable. The benefits of zinc oxide also may be realized less expensively by using as acceptor the zinc sinter which occurs in the refining of zinc. The reaction rate of zinc sinter is noticeably lower than that of zinc oxide impregnated on an inert carrier. Volatility of zinc metal and zinc sulfide prevents the use of zinc acceptors at elevated temperatures. However a lower equilibrium value of With zinc oxide as acceptor, no higher oxides or sulfates are formed during regeneration.

' During desulfurization, some of the available zinc appears as zinc metal which is volatile at the system temperature. The undesirable loss of zinc metal through volatilization may be minimized by adding small quan' tities of steam to the desulfurization zone to suppress formation of the zinc metal.

Iron oxide Iron oxide may be used as an acceptor in the present process where extensive desulfurization is not required. Reference to Figure 1 reveals that a substantial quantity of sulfur in carbonaceous solids is inorganically bound, principally in the form of iron sulfide. Removal of sulfide from the iron inherent in the carbonaceous solids cannot be effected by means of an iron oxide acceptor which possesses the same equilibrium value.. However, the iron oxide acceptor is adequate for removing the readily removable sulfur which is organically bound. Since this last-mentioned sulfur usually comprises at least 50 percent precedes the H 8 absorption.

The overali acceptor reaction can be expressed as Iron oxide-{41 5 5 iron sulfide-l-H O 'Generallyhigher temperatures in the desulfurization range of 13004600 F. are preferred where 'iron oxide is employed as the acceptor. The iron oxide may be used in the form of carefully screened iron ore;;the iron oxide may be impregnated upon an inert amphoteric oxide.

Regeneration of sulfidediron acceptor occurs in the presence of air a Y Iron sulfide-p0 iron oxides-p80 On regeneration the iron oxide acceptor forms higher oxides and sulfates in the same manner as manganese oxide, already described. These higher oxides and sul fates are undesirable in the desulfurization zone because their reduction therein consumes hydrogen without. a concomitant sulfur removal. The formation of substantial quantities of sulfate and higher oxides may be avoided by a technique similar to that described in the case of manganese. 7 I 1 7 Cobalt oxide The properties of cobalt oxide as an acceptor in -the present process are generally the same as those for iron oxide. Nickelnickel oxide Nickel oxide, impregnated upon a suitable inert carrier, also is suitable as an acceptor in the present process. The nickel acceptor is similar to the iron acceptor in that desulfurization probably occurs in two steps. Nickel oxide first is reduced to nickel metal. e Y

NiQ+H Ni+I-I O V V which in turn reacts with the hydrogen sulfide to form nickelsubsulfides, solid solutions of sulfur in nickel and finally NiS, e

Ni+H S- NiS+H The overall desulfurization reaction can be expressed NiO+H S NiS+H O Regeneration of the sulfided nickel with air occurs as follows:

' NiS-[-%O NiO+SO By regulating regeneration temperature and the supply of air to the regenerator, a portion of the nickel on the carrier may be recovered as free metal.

The free metal nickel, on returning to the desulfurization zone, permits desulfurization of carbonaceous solids without consumption of 7 hydrogen. 7

apnoea? i3 CpperCopper oxide Copper oxide may be impregnated upon an inert carrier to serve as the acceptor in the present invention Cuprous.

sulfide can be regenerated to produce free copper by limiting the supply of air to the .regenerator; The-free copper (like the free nickel just described) will :eliminatesulfur from char without an accompanyinghydrogen. consumption. The desulfurization' reactions for the freecopper and the cuprous oxide are' 2Cu+H S Cu 's l-H The reduced hydrogen consumption resulting fromusing copper as an acceptor permitscarrying .out the desulfurization reactions at temperatures as low as 1150-1200 F. without requiring an extrinsic'source-of hydrogen; The copper-copper oxide acceptor can be regenerated with oxygen at temperatures as low as 12004500? 'F'.'to:produce-a regenerated material containing'copper and copperaoxide.

Lead oxide Another suitable acceptor in therprcsentprocessfisilead oxide preferably impregnateduponan inert carrier solid. The conditions for using lead 'oxide as acceptor aresimilar to those described .herein.:for. copper-oxide. The lead oxide is probably first reducedftoa metal= which thereupon functions as an acceptor for hydrogen sulfide, forming lead sulfide.

Regeneration of the lead .oxide acceptor inthe presence of air produces'the oxide. Sulfate formation is generally small at elevated temperatures By use of adeficiency of air the acceptor may be recovered as the metal formed by the reaction Both the desulfurization and regeneration stages arepreferably carried out at low temperature; i; e., 1100 to 1500 F. where lead oxide is employed to minimize loss of the material through volatilization.

General considerations through which relatively large pellets of acceptor material (e. g., /1" diameter and larger) are showered downwardly or through which a movingbed of large pellets is caused to descend. Separation ofdesulfurized-iproduct carbonaceous. solids fromsulfided'acceptor'pellets can be accomplished by screening or elutriation, for example;

Our present process also is applicable to the .desulfurization of agglomerates formed from'sulfur containing-carbonaceous solids, such as formedbriquettes, spherical fa glomerates formed by tumbling; and the like. When-rel tively large carbonaceous'solids, such as agglomerates, are treated, we prefer to employ finelydivided acceptor, for example, acceptor having a fiuidizabl'e size:consistwhich permits its regeneration by convenient fluidized solids contacting with air. Treatment ofcarbonaceous agglomerates preferably is carried out inrotating kiln apparatus with a large stoichiometricexcess of acceptors If de sired the agglomerates may be treated at hightemperature above about 1450" F; to effect con-currentlythe desulfurizing afforded by the present inventionandalsoa calcination treatment which introduces increased strength to themgglomerates.

When i the carbonaceous solidsundergoingtreatment contain sufiicient volatile matter,- the recirculating stream of treating gases canbe eliminated- The nascent devolatilization gases alone-duringtheirbrief residencezin the desulfurization zone, will suffice to transfer sulfur-from carbonaceous solids to the acceptor, provided the-.rmixture of solids is maintainedin agitation.-

According to the provisions of. the-.: patent. statutes, we have explained the principle, preferred'construction, and mode of operation of. ourinvention and :have illustreated and described what we now consider .to represent its best embodiment. However, We desire to havetit understood that, within the scope-ofz-theappended.claims,the invention may be .practiced otherwise: than: as ispecifically illustrated and described- We claim:

1. The method. of. removing. sulfur. from: particulate carbonized zcarbonaceous solids bearingv ani-initial quantity of fixed carbon, which comprises preparingan'intimate admixture of 'said carbonaceous fSOlldS and. particulate acceptor solids which are capable. ofireactingzwith hydrogen sulfide to form solid sulfides in the.presence of hydrogen gas at a temperature above 1100 F and are capable of rejectingsulfide sulfur under oxidative conditions at elevated temperatures, subjecting ,said admixtureto treatment at a temperature above-1100 F. in the presence of hydrogen gas until aportion of the initial sulfur'has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon'of said carbonaceous solid in. said admixture .through-out said treatment at a value at least percent of said. initial quantity, separating particulate acceptorsolids containingsolid. sulfides from low sulfur carbonaceous solids, recoveringlow sulfur particulate carbonaceous solids as product containing at least 90- percent of said initial quantity of fixed carbon; subjecting said acceptor solids containing solid sulfides to elevated temperatures under oxidative conditions to eliminate therefrom sulfide sulfur, and recovering thus treated acceptor solids for reuse.

2. The method of removing sulfurfromparticulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which are capable ofgenerating-hydrogen gas by devolatilization on exposure to elevated temperatures which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids which are capable of reacting with hydrogen sulfideto form solid sulfides in the presence of hydrogen gas at a temperature above 1100" F. and are capable .of rejecting sulfide sulfur under oxidative conditions at elevated temperatures, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of. hydrogen gas at which partial devolatilization of said carbonaceous solids occurs for a period of time until a portion of the initialsulfur has been removed from .said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughoutsaid treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing solid. sulfides from low sulfur, partially devolatilized particulate carbonaceous solids, recovering low sulfur, partially devolatilized particulate carbonaceous solids as product having a fixed carbon content at least 90 percent of said initial fixed carbon content, subjecting saidiacceptor solids containing solid sulfides to elevated temperatures under oxidative conditions to eliminate therefrom sulfide sulfur, and recovering thus treated acceptor solids for reuse.

3; The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an intimate'admixture of said carbonaceous solids and particulate acceptor solids which comprise a metallic oxide capable of reacting with hydrogen sulfide to form solid sulfides in the presence of hydrogen gas at a temperature above 1100 F. and is capable of rejecting sulfide sulfur under oxidative conditions at elevated temperatures, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing solid sulfides from low sulfur particulate carbonaceous solids, recovering low sulfur carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing solid sulfide to elevated temperatures under oxidative conditions to eliminate therefrom sulfide sulfur, and recovering thus treated acceptor solids for reuse.

4. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an'intimate admixture of said carbonaceous solids and particulate acceptor solids comprising an inert porous refractory material impregnated with an oxide of a metal capable of reacting with hydrogen sulfide in the presence of hydrogen gas at a temperature above 1100 F. to form a sulfide of said metal and capable of rejecting sulfide sulfur in the presence of air at elevated temperatures to reform the oxide of said metal, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing sulfide of said metal from low sulfur particulate carbonaceous solids, recovering low sulfur carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon,

subjecting said acceptor solids containing sulfide of said 7 metal to elevated temperatures in the presence of air to convert sulfide of said metal to oxide of said metal, and recovering thus treated acceptor solids containing oxide of said metal for reuse.

5. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids containing lime, subjecting said admixture to treatment at a temperature above 1100 F. in the pres ence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing calcium sulfide from low sulfur carbonaceous solids, recovering low sulfur par ticulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing calcium sulfide to elevated temperatures in the presence of air to convert calcium sulfide to calcium oxide, and recovering thus treated acceptor solids containing calcium' oxide for reuse.

6. The method of removing sulfur from particulate said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least percent of said initial quantity, separating particulate acceptor solids containing manganese sulfide from low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing manganese sulfide to elevated temperatures in the presence of air to convert manganese sulfide to oxide of manganese, and recovering thus treated acceptor solids containing oxide of manganese for reuse.

7. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an intimate admixture of said carbonaceous solids and particulate calcined dolomite containing calcium oxide, subjecting said admixture to a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating said particulate calcined dolomite containing calcium sulfide from 'low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said calcined vdolomite containing calcium sulfide to elevated temperatures in the presence of air to convert calcium sulfide to calcium oxide, and recovering thus treated calcined dolomite containing calcium oxide for reuse.

8. The method of removing sulfur from particulate carbonized carbonaceous solids bearing'an initial quantity of fixed carbon which comprises preparing an intimate admixture from said carbonaceous solids which are below a desulfurization temperature and particulate acceptor solids which are above a desulfurization temperature whereby the said admixture is at a desulfurization temperature above 1100 F., said acceptor solids being capable of reacting with hydrogen sulfide to form solid sulfide in the presence of hydrogen gas at a temperature above 1100 F. and being further capable of rejecting sulfide sulfur under oxidative conditions at a temperature above said desulfurization temperature, maintaining said admixture at said desulfurization temperature in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solid sulfide from low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing solid sulfide to oxidative conditions at a temperature above said desulfurization temperature to eliminate therefrom sulfide sulfur, and recovering thus treated acceptor solids at a temperature above said desulfurization temperature for reuse.

9. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an intimate admixture having a desulfurization temperature above 1100 F. from said carbonaceous solids which are below said desulfurization temperature and particulate acceptor solids which are above said desulfurization temperature and which have a size consist differing from that of said carbonaceous solids whereby physical separation of the two materials is readily effected, said particulate acceptor solids comprising a major portion of a porous, abrasive resistant, inert refractory material being impregnated with a metal oxide which is capable of reacting with hydrogen sulfide in the presence of hydrogen gas at a temperature above 1100 F. to form a sulfide of said metal and capable of rejecting sulfide sulfur in the presence of air at a temperature above said desulfurization temperature to reform the oxide of said metal, maintaining said admixture at said desulfurization temperature in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids, maintaining the quantity of fixed carbon of said carbonaceous solid in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing sulfide of said metal from low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing sulfide of said metal to oxidative conditions at a temperature above said desulfurization temperature to convert sulfides of said metal to oxide of said metal and recovering thus treated acceptor solids containing oxide of said metal for reuse.

10. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon by means of treatment with particulate acceptor solids having a size consist differing from that of said carbonaceous solids whereby physical separation of the two materials may be readily effected, said acceptor solids being abrasion resistant, being capable of reacting with hydrogen sulfide in the presence of hydrogen gas at a temperature above 1100 F. to form solid sulfides, and being capable of rejecting sulfide sulfur under oxidative conditions at a temperature above said desulfurization temperature, said method comprising circulating said acceptor solids sequentially through a desulfurization zone containing hydrogen gas at a temperature above 1100 F, and through an acceptor regeneration zone containing oxygen gas at a temperature above that of said desulfurization zone, introducing said carbonaceous solids having a high sulfur content into intimate admixture with said acceptor solids entering said desulfurization zone maintaining the quantity of fixed carbon of said carbonaceous solids in said admixture throughout said desulfurization zone at a value at least 90 percent of said initial quantity, recovering from said desulfurization zone as product, separately from said particulate acceptor solids, said particulate carbonaceous solids having a low sulfur content and containing at least 90 percent of said initial quantity of fixed carbon, continuously recovering a gas containing hydrogen from said desulfurization zone and recycling at least a portion of said gas back to said desulfurization zone.

11. The method of removing sulfur from finely divided cw temperature carbonization char which comprises preparing an intimate admixture of said char which is below a desulfurization temperature and particulate acceptor solids which are above a desulfurization temperature, which are abrasion resistant and which have a size consist differing from that of said char whereby physical separation of said char from said acceptor solids may be readily effected, said acceptor solids being capable of reacting with hydrogen sulfide in the presence of hydrogen gas at a desulfurization temperature above 1100 F. to form solid sulfide and being capable of rejecting sulfide sulfur under oxidative conditions at a temperature above said desulfurization temperature, introducing said admixture into a desulfurization zone maintained at a desulfurization temperature above 1100 F. to effect partial devolatilization of said char producing devolatilization gas containing hydrogen, continuously recovering gas containing hydrogen from said devolatilization gas and recirculating at least a portion of said gas back to said desulfurization zone, maintaining said admixture in said desulfurization zone until a portion of the initial sulfur of said char has been removed therefrom, maintaining the quantity of fixed carbon of said char in said admixture at a value at least percent of the quantity of fixed carbon originally in said admixture, separately recovering from said desulfurization zone firstly a low sulfur content, partially devolatilized finely divided char as product containing at least 90 percent of the quantity of fixed carbon originally in said admixture, and secondly particulate acceptor solids containing sulfide sulfur, introducing said acceptor solids containing sulfide sulfur to an acceptor regenerator zone containing oxygen gas at a temperature above said desulfurization temperature for removal of sulfide sulfur therefrom and recovering from said acceptor regenerator zone said solid acceptor for reuse in the process.

12. The method of claim 11 in which the particulate acceptor solids comprise calcined dolomite.

13. The method of claim 11 in which the particulate acceptor solids comprise a porous, inert, refractory material impregnated with 2 to 20 percent of calcium oxide by weight.

14. The method of claim 11 in which the particulate non-caking acceptor solids comprise a porous, inert, refractory oxide impregnated with 2 to 20 percent of manganese oxide by weight.

15. The method of removing sulfur from particulate carbonized carbonaceous solids bearing an initial quantity of fixed carbon which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids comprising a major portion of an inert, porous, refractory material and a minor portion of a metal oxide selected from the class consisting of oxide of calcium, manganese, iron, zinc, copper, nickel, cobalt and lead, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids and a portion of said metal oxide has been converted to a metal sulfide, maintaining the quantity of fixed carbon of said carbonaceous solids in said admixture throughout said treatment at a value at least 90 percent of said initial quantity, separating particulate acceptor solids containing said metal sulfide from low sulfur carbonaceous solids, recovering low sulfur particulate carbonaceous solids as product containing at least 90 percent of said initial quantity of fixed carbon, subjecting said acceptor solids containing said metal sulfide to elevated temperatures under oxidative conditions to convert said metal sulfide to metal oxide, and recovering thus treated acceptor solids containing metal oxide for reuse.

16. The method of claim 1 in which the carbonized carbonaceous solids comprise pitch coke.

17. The method of claim 1 in which the carbonized carbonaceous solids comprise petroleum coke.

18. The method of claim 1 in which the carbonized carbonaceous solids comprise the solid residue obtained by low temperature carbonization of lignite.

19. The method of claim 1 in which the carbonized carbonaceous solids comprise char obtained from low temperature carbonization of caking bituminous coal.

Rosen et al. Oct. 16, 1934 Gorin et a1. Sept. 13, 1955 

1. THE METHOD OF REMOVING SULFUR FROM PARTICULATE CARBONIZED CARBONACEOUS SOLIDS BEARING AN INTIAL QUANTITY OF FIXED CARBON, WHICH COMPRISES PREPARING AN INTIMATE ADMIXTURE OF SAID CARBONACEOUS SOLIDS AND PARTICULATE ACCEPTOR SOLIDS WHICH ARE CAPABLE OF REACTING WITH HYDROGEN SULFIDE TO FORM SOLID SULFIDES IN THE PRESENCE OF HYDROGEN GAS AT A TEMPERATURE ABOVE 1100* F. AND ARE CAPABLE OF REJECTING SULFIDE SULFUR UNDER OXIDATIVE CONDITIONS AT ELEVATED TEMPERATURES, SUBJECTING SAID ADMIXTURE TO TREATMENT AT A TEMPERATURE ABOVE 1100* F. IN THE PRESENCE OF HYDROGEN GAS UNTIL A PORTION OF THE INITIAL SULFUR HAS BEEN REMOVED FROM SAID CARBONACEOUS SOLIDS, MAINTAINING THE QUANTITY OF FIXED CARBON OF SAID CARBONACEOUS SOLID IN SAID ADMIXTURE THROUGHOUT SAID TREATMENT AT A VALUE AT LEAST 90 PERCENT OF SAID INITIAL QUANTITY, SEPARATING PARTICLE ACCEPTOR SOLIDS CONTAINING SOLID SULFIDES FROPM LOW SULFUR CARBONACEOUS SOLIDS, RECOVERING LOW SULFUR PARTICULATE CARBONACEOUS SOLIDS AS PRODUCT CONTAINING AT LEAST 90 PERCENT OF SAID INITIAL QUANTITY OF FIXED CARBON SUBJECTING SAID ACCEPTOR SOLIDS CONTAINING SOLID SULFIDES TO ELEVATED TEMPERATURES UNDER OXIDATIVE CONDITIONS TO ELIMINATE THEREFROM SULFIDE SULFUR, AND RECOVERING THUS TREATED ACCEPTOR SOLIDS FOR REUSE. 